1. Field of the Invention
The invention concerns structural urethane adhesives comprising amide polyols, including 2-component aliphatic urethane adhesive systems. The adhesives adhere to a wide variety of substrates. For example, the adhesives can be used as grout material in tile applications, particularly ceramic tile applications.
2. The Related Art
Effective structural adhesives require the ability to adhere to a variety of different types of substrate materials and provide structural integrity to a construction. Adhesives that adhere equally well to metals, such as aluminum, wood or other fibrous materials and ceramic or glass materials would provide an exemplary structural adhesive.
Floor tiles are generally installed by mortaring tile directly onto a wood or cement floor and then grouting the tile with a water-based cementitious grout. Water-based cementitious mortars and grouts may perform poorly in very wet applications as well as with tiles that are not moisture sensitive. For example, flooring made of water swellable materials such as particle board cannot be easily used with water-based cements, and certain types of colored marble tiles swell when exposed to water. Thus great care must be taken when installed with a water-based mortar or grout. Also, the flooring and tiles may be adversely affected by moisture due to location of the flooring installation, i.e. sub-grade flooring installations or installations in kitchens or baths to name a few.
Polymeric grouts are useful for flooring installations and tiles that may be adversely affected by moisture. Further, tile installation, with polymeric grout having excellent moisture resistance can be walked on within 2 to 24 hours depending upon the polymeric grout used. This is faster than using conventional techniques with water-based cementitious grout which can take days before the tile can be put into service. For example, epoxy-based adhesives which are commercially available and cure within a day are generally preferred in wet conditions. Water-based polyurethane adhesives also exhibit good grout properties though they are not structural adhesives and can take up to 24 hours before light foot traffic can resume. Solvent-less 2-component aromatic urethane grouts are a good alternative to the epoxy grouts as they are faster curing and have high strength and flexibility but tend to yellow on exposure to sun. On the other hand, 2-component aliphatic polyurethane structural adhesives cure rapidly and exhibit non-yellowing properties and thus would be preferred for flooring and tile installations. However, typical aliphatic polyurethane structural adhesives do not adhere as well to ceramic substrates and have poor strength properties.
All parts and percentages set forth in this specification and the appended claims are on a weight-by-weight basis unless otherwise specified.